The use of inkjet printing systems in offices and homes has grown dramatically in recent years. The growth can be attributed to drastic reductions in cost of inkjet printers and substantial improvements in print resolution and overall print quality. While the print quality has drastically improved, research and development efforts continue toward improving the permanence of inkjet images because this property still falls short of the permanence produced by other printing and photographic techniques. A continued demand in inkjet printing has resulted in the need to produce images of high quality, high permanence, and high durability, while maintaining a reasonable cost.
In inkjet printing, the inkjet image is formed on a print medium when a precise pattern of dots is ejected from a drop-generating device known as the printhead. The typical inkjet printhead has an array of precisely formed nozzles located on a nozzle plate and attached to an inkjet printhead array. The nozzles are typically 30 to 40 micrometers in diameter. The inkjet printhead array incorporates an array of firing chambers that receive liquid ink, which includes pigment-based inks and/or dye-based inks dissolved and/or dispersed in a liquid vehicle, through fluid communication with one or more ink reservoirs. Each chamber has a thin-film resistor, known as a firing resistor, located opposite the nozzle so that the ink can collect between the firing resistor and the nozzle. Upon energizing of a particular firing resistor, a droplet of ink is expelled through the nozzle toward the print medium to produce the image. The printhead is held and protected by an outer packaging referred to as a print cartridge or an inkjet pen.
When inks of different colors are printed next to each other on bond paper, copier paper, and other media, bleeding could result. Bleeding occurs as colors mix both on the surface of the paper being printed on and in the paper. The term “bleed” is defined as follows. When inks of two different colors are printed next to each other, it is desired that the border between the two colors be clean and free from the invasion of one color into the other. When one color does invade into the other, the border between the two colors becomes ragged, and this is called bleed. This is in contradistinction to uses of the term “bleed” in other situations, which often defines “bleed” in the context of ink of a single color following the fibers of the paper. In addition, when dye-based inks are printed adjacent to pigment-based inks, the dye-based ink may invade the pigmented ink causing a whitish edge to form in the pigmented ink. This is known as halo, and is most often observed when dye-based color inks are printed adjacent to pigment-based black inks.
Prior solutions to control bleed have largely involved the use of heated platens or other heat sources and/or special paper. Heated platens add cost to the printer. Special paper limits the user to a single paper, which is of a higher cost than a plain paper. Another way to reduce bleed involves increasing the penetration rate of the ink into the paper. However, increasing the penetration rate reduces the edge acuity (lowers the print quality of the print). Therefore, alternate bleed control mechanisms are needed.